It's impossible to predict. The thickness and composition of the walls, other furniture and other sources of signal interference are just some of the unknown variables.
If you can find a retailer who will let you try the kit first, or will give a guarantee that it will work....
What would definitely work over that range is Ethernet cable. If you have stud walls, make a small hole at the bottom of the wall, drop the wire down from the loft and fish it out through the hole with a coat hanger.
For solid walls, consider running it down the side of a doorway or a corner of the room, or under the floorboards if it is a suspended floor.